Mega 2560 TX/RX LED hanging

Using Arduino IDE 1.x
1

I've been trying to find information about this on the ardunio website or in the forums, but without success.

What does it mean if both TX and RX LEDs on the Mega 2560 card is constant lit?
I'm having problems with my 2560 that it stopps communicating with me over serial interface (USB, Window7 64bit, .Net), and every time both TX and RX lights are on until I unplug and plug the USB cable.

Ideas?

I'm not using an external power supply, could that be a reason?

2

Have you already try to upload an example Sketch from the IDE?

3

HugoPT:
Have you already try to upload an example Sketch from the IDE?

Yes, I've run several different sketches.

Lately though, the sketch upload has been starting to hand and never finish. If I then exit the arduino GUI and try again, the COM-port is in use.

It looks like in the screenshot attached. Could this be due to long USB cable (standard 2m + 5m extension)?

Arduino_upload.png
Arduino_upload.png500×600 29.3 KB